The purpose of this study is 1) to determine the pharmacokinetics of compound VX-105 (arginine butyrate) in children with sickle cell anemia; 2) to determine if it is safe to give compound VX-105 infusions in children with sickle cell anemia; and 3) to determine the efficacy of infusions with compound VX-105 on hematologic parameters in children with sickle cell anemia.